The road less traveled: Alternative pathways for action-verb processing in Parkinson disease

SOFÍA ABREVAYA; DAVID PINEDA; ANDRÉS VILLEGAS; SOL FITTIPALDI; NATALIA TRUJILLO; OMAR BURITICA; ADOLFO M. GARCÍA; DIANA GOMEZ; AGUSTIN IBÁÑEZ; LUCAS SEDEÑO; FRANCISCO LOPERA; CATALINA BUSTAMANTE; RICARDO PAUTASSI

Habana

Congreso; 18th IOP World Congress; 2016

Action verbs involve activations along motor brain networks. In Parkinson?s disease (PD), damage to the latter is associated with difficulties to access such words. However, patients are not fully incapable of processing them, as their performance is far from floor level. Here we tested the novel hypothesis that action-verb processing in PD may rely on coarser-grained, non-motor semantic circuits. Seventeen pre-demented PD patients and 15 healthy controls listened to action verbs and nouns as they underwent fMRI scanning. Functional connectivity was analyzed considering seeds differentially engaged by action (putamen, M1) and non-action (posterior superior temporal lobe) words. The putamen seed showed reduced connectivity withinthe basal ganglia in patients for both lexical categories (p = .005 for verbs, and p = .03 for nouns).. However, only action verbs involved differential cortical networks in each group. Specifically, analysis of the M1 seed revealed greater connectivity with posterior (cingulate) and anterior (inferior frontal) regions for patients (p = .03) and controls (p = .05), respectively (there being no differences in the temporal seed). Moreover, the patients? level of basal ganglia atrophy was positively associated with their reliance on M1-posterior connectivity during action-verb processing. PD patients processed action-verbs via non-motor cortical networks arguably involved in amodal semantic processing. Such circuits would afford alternative pathways to process word meaning when default embodied mechanisms are disturbed. Moreover, the greater the level of basal ganglia atrophy, the greater the patients? reliance on this alternative route. These results offer new insights into compensatory neurofunctional mechanisms operative to accomplish high-order tasks in PD.